class Solution(object):
    def reverseString(self, s):
        """
        :type s: List[str]
        :rtype: void Do not return anything, modify s in-place instead.
        """
        h = len(s) - 1
        l = 0
        while l < h:
            (s[l], s[h]) = (s[h], s[l])
            l += 1
            h -= 1

s = Solution()
L = ["h","e","l","l","o"]
s.reverseString(L)
print(L)
